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J Biomech. 2014 Jul 18;47(10):2452-9. doi: 10.1016/j.jbiomech.2014.04.014. Epub 2014 Apr 18.

Human L3L4 intervertebral disc mean 3D shape, modes of variation, and their relationship to degeneration.

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University of Pennsylvania, Philadelphia, PA 19104, USA.
University of Pennsylvania, Philadelphia, PA 19104, USA; GE Healthcare, Florence, SC 29501, USA.
Penn State College of Medicine, Hershey, PA 17033, USA.
University of Pennsylvania, Philadelphia, PA 19104, USA; University of Delaware, 125 East Delaware Ave Newark, Newark, DE 19716, USA. Electronic address:


Intervertebral disc mechanics are affected by both disc shape and disc degeneration, which in turn each affect the other; disc mechanics additionally have a role in the etiology of disc degeneration. Finite element analysis (FEA) is a favored tool to investigate these relationships, but limited data for intervertebral disc 3D shape has forced the use of simplified or single-subject geometries, with the effect of inter-individual shape variation investigated only in specialized studies. Similarly, most data on disc shape variation with degeneration is based on 2D mid-sagittal images, which incompletely define 3D shape changes. Therefore, the objective of this study was to quantify inter-individual disc shape variation in 3D, classify this variation into independently-occurring modes using a statistical shape model, and identify correlations between disc shape and degeneration. Three-dimensional disc shapes were obtained from MRI of 13 human male cadaver L3L4 discs. An average disc shape and four major modes of shape variation (representing 90% of the variance) were identified. The first mode represented disc axial area and was significantly correlated to degeneration (R(2)=0.44), indicating larger axial area in degenerate discs. Disc height variation occurred in three distinct modes, each also involving non-height variation. The statistical shape model provides an average L3L4 disc shape for FEA that is fully defined in 3D, and makes it convenient to generate a set of shapes with which to represent aggregate inter-individual variation. Degeneration grade-specific shapes can also be generated. To facilitate application, the model is included in this paper׳s supplemental content.


Degeneration; Intervertebral disc; Magnetic resonance imaging; Morphometry; Statistical shape model

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